The present invention, in some embodiments thereof, relates to a rectifying antenna device and, more particularly, but not exclusively, to a rectifying antenna device operating in the infrared (IR) and visible light.
There are many applications in which it is useful to beam energy from an energy production location to a destination at which the energy will be used. The “beamed” energy is typically microwave or radiofrequency. However, many applications for the energy require direct current (DC) power.
A rectifying antenna, also known as a “rectenna” is an electrical device which facilitates the conversion of microwave and radiofrequency alternating current (AC) radiation into DC electrical power. The conversion takes place by a rectifying diode which is incorporated into the antenna. In operation, the antenna gathers electromagnetic energy at a frequency consistent with its size and shape, and the diode rectifies that energy into DC voltage.
The rectenna may be used as the receiving terminal of a power transmission system. In this configuration, the terminal may deliver DC power to a load where physical transmission lines are not feasible. The power delivery may be through free space. The rectenna may also be useful in applications where DC power needs to be distributed to a large number of load elements that are distributed spatially.
Traditionally, rectennae utilize a semiconductor diode or large vacuum diode to rectify electromagnetic waves, with frequencies ranging up to the mm-waves band, to direct current. Also known (see e.g., U.S. Pat. No. 5,043,739), are rectennae utilizing a first field emission diode for rectifying a current flow.
Recently, periodic and random arrays of multi-walled carbon nanotubes (MWCNTs) have been synthesized on various substrates. Each nanotube in the array is a conducting rod of about 10-100 nm in diameter and 200-1000 nm in length. Therefore, one can view interaction of these arrays with the electromagnetic radiation as that of an array of dipole antennas. MWCNTs arrays have been studied in order to determine the antenna-like interactions, since the most efficient antenna interaction occurs when the length of the antennas is of the order of the wavelength of the incoming radiation.
U.S. Published Application No. 20070240757 discloses a solar cell which includes a planar substrate having a conductor layer below a semiconductor layer, and an array of carbon nanotubes engaging the semiconductor layer at a first end and comprising an optical antenna at a second end. A layer of a rectifying material is deposited onto the nanotubes.
Additional background art includes Weiss et al., “A Novel Nanowire/Nanotube Device Acting as Both Antenna and Rectifier for Solar Energy Conversion up to the Optical,” conference abstract, Electronic Materials Conference, 2008; Kempa et al., “Carbon Nanotubes as Optical Antennae,” Adv. Mater. 2007, 19, 421-426; U.S. Pat. No. 7,132,994, U.S. Published Application No. 20070240757, Abrams et al., “A Complete Scheme for Creating Large Scale Networks of Carbon Nanotubes,” Nano Letters, 7 (2007) 2666-2671; U.S. application Ser. No. 12/155,089; Slepyan et al.,” Theory of optical scattering by achiral carbon nanotubes and their potential as optical nanoantennas,” Phys. Rev. B. 73, 195416 (2006), B. Berland, “Photovoltaic Technologies Beyond the Horizon: Optical Rectenna Solar Cell,” ITN Energy Systems, Inc. Littleton, Colo. (2003); and Levy Yeyati et al., “On the theory of difference frequency generation and light rectification in the scanning tunneling microscope,” J. Phys: Condens. Matter 4 (1992) 7341-7354.